#include<bits/stdc++.h>
#define ONLINE_JUDGE
#define ll long long
#define ull unsigned long long
using namespace std;

const int N = 1e6 + 10, INF = 0x3f3f3f3f;

int n;
string s;
int t[N];

void solve()
{
    cin >> n >> s;
    s = " " + s;
    for (int i = 1;i <= n;i++)
        t[i] = t[i - 1] + (s[i] == '1' ? 1 : -1);

    int sum = count(s.begin(), s.end(), '1');
    int ans = 0, mi = 0;
    for (int r = 1;r <= n;r++) {
        mi = min(mi, t[r]);
        ans = min(ans, mi - t[r]);
    }
    cout << sum + ans << '\n';
}

signed main()
{
    // ios::sync_with_stdio(0);
    // cin.tie(0);cout.tie(0);
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    int T = 1;
    cin >> T;
    for (int i = 1;i <= T;i++) {
        solve();
    }
}